The raw materials situation no longer permits the rejection of curved sawing timber, which accounts for approximately 33% of the timber available for sawing. The technique of "curve sawing" in which the saw cut or cuts are essentially similarly curved as the centre line of the piece of timber, produces boards and planks which are broadly equivalent to boards and planks obtained from completely straight pieces of timber. However, existing sawing equipment is largely designed to saw straight pieces of timber. The purpose of the invention is to achieve a simple and effective arrangement for inserting straight or curved blocks which are machined or are to be machined on at least two opposite sides.